Automatic ice cube machines are widely used in restaurants, bars, hotels, etc. Such commercial machines typically form ice cubes by freezing a flowing stream of water on the chilled evaporator portion of a refrigeration system. After the ice has been formed to the desired thickness, the evaporator is heated, thereby melting the bond between the ice and the evaporator and allowing the ice to then fall or be pushed into an ice holding bin below. Heating of the evaporator is typically accomplished using a defrost cycle or "hot gas defrost," whereby hot refrigerant from the compressor is caused to bypass the condenser and go directly into the evaporator. The hot gas defrost cycle ends after the ice cubes have fallen away from the evaporator.
Such a hot gas defrost cycle adversely affects the capacity and energy efficiency of the ice machine. The ice making capacity is significantly reduced because: (1) the ice machine cannot produce ice while it is in a defrost cycle, (2) it actually melts some ice during this cycle, and (3) the heat added to the evaporator during hot gas defrost must be removed from the evaporator before freezing can start again--which means that the machine's refrigerating capacity is being used to remove heat added during defrost rather than to make ice. Also, because the ice making machine is consuming energy during the defrost process but is not making ice, the energy efficiency is significantly lower than that of an ice machine with no defrost cycle.
The capacity and energy efficiency of an ice making machine are also affected by the refrigeration system's condensing and evaporating temperatures. It is well known that raising the condensing temperature and/or lowering the evaporating temperature in a refrigeration system lead to a reduction of the heat transfer output and efficiency of the system. In order to quickly heat the evaporator for a fast defrost, cube making ice machines often have a higher condensing temperature than would otherwise be required. This also leads to lower capacity and efficiency.
In addition, the evaporating temperatures typically used on cube making ice machines are often less than optimal. This is due primarily to the thickness of the ice produced. Because ice is a relatively poor conductor of heat, it tends to insulate the evaporator surface more as it grows thicker. To maintain the desired rate of heat transfer, the evaporating temperature must therefore drop to overcome this insulating effect. The thicker the ice cubes, the more the evaporating temperature must drop. This drop in evaporating temperature contributes further to a reduction in ice producing capacity and energy efficiency.
Another disadvantage of ice machines using hot gas defrost is their reduced service life. An ice machine which utilizes a defrost cycle constantly cycles between warm and cold. This constant thermal cycling causes the main components to wear out faster than they would otherwise.
Yet another drawback of most existing ice cube making machines is their inability to produce ice cubes of various shapes and sizes. An ice machine with the ability to make ice cubes of various shapes (such as the shape of a company's logo, for example) would have an advantage in the marketplace over traditional ice machines. This ability would also allow ice cubes to be designed with various desirable properties (e.g., slow melting ice cubes, quick melting ice cubes, no-splash ice cubes, etc.).
Various machines and methods for making ice have been available heretofore. For example, U.S. Pat. Nos. 2,683,356 and 2,683,359 to Charles M. Green, Jr. describe an ice making method and apparatus whereby ice is formed on deformable refrigerated plates that are submerged under water. After a layer of ice has formed on the refrigerated plates, the plates are alternately flexed between a concave and a convex shapes. This causes the ice layer on the plate to be partially broken away from the plate forming small pockets between the plates and the ice layer. These pockets then fill with a thin layer of water that freezes and becomes part of the total ice layer. As the flexing of the plates is repeated, many of these thin layers are laminated together building up a fairly thick piece of ice. Eventually, with repeated flexing of the deformable plates, irregularly shaped pieces of ice, or "cubes," break free from the plate. If the process is continued without removal of these ice pieces, a large block of ice is formed as all the small pieces freeze together. While Green's method will produce ice without the use of a defrost cycle, it will not produce clear, uniformly shaped cubes. Rather, the cubes produced will be cloudy and randomly shaped both in thickness and in cross-sectional shape because the water that is frozen has been trapped in pockets between previously frozen layers of ice and the freezing surface. Since no water flow is possible in these pockets, the impurities and dissolved gases in the water cannot be removed----the impurities are simply frozen into the ice layer resulting in cloudiness. The irregular shape of the ice pieces produced results from the lack of any type of control over the ice layer thickness or how the ice breaks free from the refrigerated plates.
Flaker-type ice machines do not utilize a hot gas defrost cycle; but cannot make cubes, much less cubes of various predetermined configurations.
The primary objective of this invention is to provide a machine or apparatus for making hard, clear, uniformly shaped ice in various configurations, both cube and noncube-shaped, which does not require hot gas defrost and which thus provides greater ice producing capacity, greater energy efficiency and longer service life than conventional cube making ice machines. By eliminating the hot gas defrost, the condenser can operate at a lower, more efficient condensing temperature. A high condensing temperature will not be required to facilitate a fast defrost.
Another primary objective of this invention is to provide a machine or apparatus for making clear ice in various configurations by laminating together thin layers of ice. By making the ice in thin layers, the insulative effect of the ice is minimized and the thermal efficiency is improved. Lamination of thin ice layers into larger cubes still allows them to be made to the desired size and shape. Improving thermal efficiency also allows a decrease in the freezing surface area needed for a given ice producing capacity. This surface area reduction in turn helps reduce the machine cost. Because of the higher thermal efficiency, a higher, more efficient, evaporating temperature can be used.
A further object of this invention is to provide a machine or apparatus which can produce clear, uniformly shaped ice cubes of virtually any desired cross-sectional shape and virtually any desired thickness.
A further object of this invention is to provide a method of efficiently and continuously freezing liquids (including, but not limited to water) into their solid form, which does not require a defrost cycle and also minimizes the insulative effect of the frozen layer.